Why Your St. Augustine Lawn Is Browning (It's Probably Not Drought)

St. Augustine goes brown in patches for one of three reasons: chinch bugs, over-watering, or not enough sun. Ninety percent of the calls Port St. Lucie Landscaping Pros gets in July and August are chinch bugs. They throw a better party in your lawn every August than most people throw in their backyard.

The Chinch Bug Tell

Here's the field test we use on every call. Kneel down at the edge of a brown patch, where dead grass meets green, and pull the dead blades back so you can see the soil line. Chinch bugs are small, black-and-white, and easy to miss if you're not looking right at the base of the turf. If you see them moving, that's your answer. If the soil underneath is bone dry and nothing's crawling, you're probably looking at drought stress or a dry irrigation zone instead.

Chinch bugs love hot, dry, sun-baked turf. That's why the peak season for damage in Port St. Lucie runs May through September, and why full-sun lawns get hit harder than shaded ones. Left alone, they can take out a section of St. Augustine in two to three weeks.

Why Homeowners Get This Wrong

A brown patch in August looks exactly like a thirsty lawn, so the instinct is to run the sprinklers longer. That doesn't slow chinch bugs down at all, and in sandy soil it can actually make things worse. (This is one I say on nearly every August call: more water isn't the fix, and sometimes it's the opposite of the fix.)

On the flip side, more lawns in our sandy Port St. Lucie soil die from over-watering than from actual drought. So the two most common causes of a brown lawn call for opposite responses, and guessing wrong costs you either a dead lawn section or a soggy one that starts rotting at the roots.

What to Do Once You've Confirmed Chinch Bugs

Treat the affected area and a buffer around it

Chinch bug damage spreads outward from the original patch. Treatment needs to cover a few feet beyond the visible brown edge, not just the dead grass itself, or you'll be back out here in two weeks treating the same infestation's next ring.

Mow at the right height for the season

St. Augustine should sit at 3.5 to 4 inches in summer and 2.5 to 3 inches in winter. Mowing too short in peak chinch bug season stresses the turf further and makes it more attractive to them, not less.

Check your irrigation schedule, separately

Don't touch the sprinkler schedule to fight chinch bugs. Handle the pest and the watering as two separate problems. If you haven't reprogrammed your controller since winter, that's worth doing on its own schedule. Our guide on how often to actually run your sprinklers covers that separately.

When It Might Be Time to Reconsider the Turf

If a full-sun section of the yard fights chinch bugs every single summer no matter what you do, that's a sign the turf and the sun exposure don't match. St. Augustine is not always the right call, even though it's what people picture when they think "Florida lawn." We've walked plenty of Port St. Lucie yards where Bahia would hold up better in the exact spot that keeps browning out.

If you'd rather read the university research than take a landscaper's word for it, the University of Florida IFAS Extension publishes a chinch bug identification and control guide that matches everything we see in the field.

Related Reading

• Bahia vs. St. Augustine: Which Grass Belongs in Your Yard
• How Often Should You Really Run Your Sprinklers in Port St. Lucie?
• Lawn Maintenance in Port St. Lucie

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